Change some module names:
* mailmanclient.restobjects.list_archiver -> mailmanclient.restobjects.archiver
* mailmanclient.restobjects.list -> mailmanclient.restobjects.mailinglist
Fix imports for the above two changes and export all the classes under
restobjects to top level mailmanclient so that they are now a part of the public API.

This commit changes the default test runner from nose2 to mailman.client. It
also adds the functionality that was previously implemented to run tests using
vcrpy and nose2 using pytest plugins.
pytest-vcr can be used to run tests using VCR.py and adds a custom command line
option --vcr-record-mode which can be used to change the recording mode for the
VCR.py.

- Remove several redundant files labeled as index or readme.
- Add NEWS file to the toctree.
- Move conf.py to the project root.
- Set README.rst as the master doc for documentation
- Remove epub related settings from conf.py
- Set README.rst as the long description.
- Fix linting errors in setup.py and conf.py.